The FDNY is taking one more step toward diversifying its ranks: the completion of women’s bathrooms and locker rooms in all city firehouses, at a cost of about $77 million over 14 years.

FDNY Commissioner Daniel Nigro plans to announce that the agency has completed the last leg of the effort — a three-year, $47 million construction program in 47 firehouses — when he swears in 317 new probationary firefighters, including nine women, on Monday.

“Our current women firefighters, and the many more we are actively recruiting to join the department, deserve this,” Nigro said. “It could not have been possible without the city’s commitment of capital funds three years ago to complete the most difficult construction projects.”

Of more than 10,000 uniformed firefighters, the FDNY now employs 58 female firefighters and officers — not counting the nine probationary officers. About 200 female FDNY EMS workers are set to take an exam this week to become firefighters.

The city has been working on adding women’s bathrooms and locker rooms for more than a decade. Since 2002, it has spent $77 million on updating 98 of its 214 firehouses.

Manhattan Borough President Gale Brewer said the cost of the new bathrooms “should be looked at,” but that there is no question adding them was necessary.

“It’s important to do this,” she said.

City Councilwoman Liz Crowley (D-Queens) said the cost is worth it, despite the relatively small proportion of women in the FDNY’s ranks.

“If you want a department that’s welcoming to all sexes, you want to make sure you have changing areas for both,” she said.